AP Photo
Israeli Border Police take position during clashes in Jerusalem's Old City Tuesday. Clashes erupted during a protest in support of Maysara Abu Hamdiyeh, 64, who was serving a life sentence for his role in a foiled attempt to bomb a busy cafe in Jerusalem in 2002, and died Tuesday of cancer in an Israeli jail. Tensions are high in Israeli lockups where thousands of Palestinian security prisoners are being held.

JERUSALEM — Israeli-Palestinian tensions rose sharply Wednesday, with a resumption of clashes over the Israel-Gaza border as Palestinian prisoners in Israeli jails declared a three-day hunger strike to protest the death Tuesday of a fellow inmate, a death that the Palestinians blamed on Israel.

In response to rockets fired from Gaza into southern Israel, apparently in support of the Palestinian prisoners, the Israeli military said it carried out an airstrike in Gaza late Tuesday night, its first since a cease-fire that ended eight days of fierce cross-border fighting in November. Warplanes struck two open areas in northern Gaza, causing no damage or casualties, the military said.

Sami Abu Zuhri, a spokesman for Hamas, the Islamic militant group that controls Gaza, called the airstrikes a clear violation of the cease-fire.

“We call on international parties to intervene immediately to end the Israeli escalation and also the violations against the prisoners,” he said in a statement.

The rocket fire from Gaza was the third such violation of the cease-fire brokered by Egypt in November, evidence of its fragility.

An Islamic extremist group in Gaza, the Mujahadeen Shura Council — Environs of Jerusalem, claimed responsibility for Tuesday’s rocket fire, saying in a statement that it was in support of the Palestinian prisoners in Israeli jails. The group criticized other Palestinian factions for their inaction on the prisoner issue.

On Wednesday morning, Gaza militants fired two more rockets into southern Israel. One landed at the entrance of the Israeli border town of Sderot, according to the police, and the other fell in open ground. Neither caused injuries.

The tensions in the south came amid signs in the north of increasing spillover from Syria’s bloody civil war. The Israeli military destroyed a Syrian post with tank fire Tuesday night after shots were fired from the Syrian side at an Israeli army jeep in the Israeli-held Golan Heights. Earlier that day, a mortar shell from Syria sailed over the Israeli-Syrian cease-fire line and crashed into an open field, according to the Israeli military.

The U.N. special coordinator for the Middle East peace process, Robert H. Serry, called the situation volatile and said it was “of paramount importance to refrain from violence in this tense atmosphere and for parties to work constructively in addressing the underlying issues.”

“The renewed violations of the cease-fire risk undermining the `understanding’ reached between Israel and Gaza on 21 November, and unraveling the gradual but tangible improvements achieved since then in the easing of the closure and the security situation in Gaza and southern Israel,” he said in a statement.

In a statement Wednesday referring to the fire from both Gaza and Syria, Israel’s defense minister, Moshe Yaalon, said, “We will not allow shooting of any sort, even sporadic, toward our citizens and our forces.”

He added, “As soon as we identify the source of the fire, we will take it down without hesitation, as we did last night and in previous cases.”